Long-reach boom pumps and bulk material conveyors at power plant construction site

RWE Power AG in Hamm, Westphalia, is investing around EUR 2 billion in the construction of one of the world’s most efficient coal power plants with a total output of 1,600 Megawatts. The placement of around 250,000 m³ concrete of different property classes and consistencies is predominantly carried out using Putzmeister truck-mounted concrete pumps with up to 62 m placing boom height and two stationary PM placing booms. But a Telebelt TB 130 telescoping conveyor belt is also used on the vast construction site to deliver the different bulk materials.

The client has commissioned ALPINE Bau Deutschland AG (Industrial and Power Plant Construction, Dortmund branch) with the execution of the extensive earth, concrete and construction work for the two new power plant blocks “D” and “E” (order volume EUR 135 million). The two-block power plant with 2 x 800 megawatt power is being constructed on the site of a previously planned nuclear power plant and next to the high temperature reactor THTR-300, which has been shut down since September 1989.

The construction of the new power plant includes a building complex of engine and boiler houses, switching system buildings and water centre, four stair towers, seven silos with up to 10,000 m³ capacity for limestone, cement and ash as well as two 165 m high cooling towers.

The order to deliver over 220,000 m³ of concrete was received by the concrete pumping service BEKA in Kerpen. Crucial in the assignment was the fleet composition of the pumping service, which consists of over 40 truck-mounted concrete pumps. Thus, in addition to machines from the 20, 30 and 40 metre class, BEKA also has three M 52-5s, three M 58-5s and two M 62-6s. Due to the vast boom lengths and large working range, made possible by flexible 5 and 6 arm technology, BEKA’s long-reach boom pumps gave it a crucial advantage in the invitation to tender. In addition, there was the possibility of supporting the large 5 and 6-axle trucks in OSS mode on one side, if the construction site conditions allow for this.

The extensive concreting began in spring 2008. For the production of the bottom plate, which is 5 m thick in places, up to 6,500 m³ concrete (C35/45) were integrated wet in wet. To complete the numerous walls, floors and beams, the Putzmeister pumps are used here almost daily. On one of our visits, we met BEKA machine operator Ricco Lemm, “My M 58 is equipped with all the electronic extras offered by Putzmeister, such as familiar systems like EBC, EOC, EPS. If you – like me now – are standing on scaffolding at a height of 20 m, the additional functions are practical, such as being able to switch the vibrator on the hopper on and off by radio remote control, and then the graphical display on the remote control shows me all the important information at all times – down to the current fluid temperature!”

Ricco Lemm is often at the power plant construction site with the M 58-5. Today he is pumping concrete with a 16 mm maximum particle size (C30/37) into the wall formwork of a switching system building. Due to the narrow reinforcement, he has switched the bottom part of his 2-part end hose for a tapering and an 80 mm end hose piece. The squeeze valve – also activated via the radio remote control - remains connected to the “1 metre piece”, the upper part of the split end hose. When the boom is swung over the formwork, the valve squeezes the end hose together with compressed air, so that no concrete remains inside.

An interesting interaction between truck-mounted concrete pumps and stationary concrete placing booms can be seen during concreting of the power houses: The two PM stationary booms with 32 m horizontal reach are supported on a tubular column, or on a lattice tower, which is extended to up to 55 m in height as the construction progresses. Via a special tube support system, the delivery line is secured on the lattice tower. It is supplied with concrete at the bottom end by one of the BEKA truck-mounted concrete pumps.

Both the outer walls of the four stair towers, which are up to 120 m high, and the seven silos, which are up to 70 m high, are constructed using the sliding formwork procedure. It is important when concreting with sliding formwork that the concrete composition is adapted to the respective outside temperature and sliding speed. Dipl.-Ing. Andreas Michnik, head of work preparation at the construction site said: “As the concrete is placed round the clock here, but only relatively small placement jobs are required, we work with a crane bucket. When using pumps, the concrete would otherwise set in the long delivery line!”

The two new power plant blocks of RWE Power AG in Hamm-Uentrop will be fired with coal and petrol coke. With an efficiency of approx. 46%, the new two-block plant will be one of the most modern and efficient coal power plants in the world. Blocks “D” and “E” should be connected to the grid by the start of 2012, and blocks “A” and “B” which have been in service since 1962/63 (output per 160 Megawatt) will be shut down.